07 Airport Pavt Design[1]

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By laurent Porot

Technology Implementer,Shell Bitumen Sustainable development

Airport Pavement Design

Airport Workshop Lafarge/Shell

10th July 2007, London


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Airport Workshop Lafarge/Shell, 10th of July 2007 Londo

Airport Pavement Desig

Agenda

1. Background2. What are the key parameters for airport pavements

3. What about pavement design

4. What is new in airport pavement engineering

5. Conclusions


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1. Background

2. What are the key parameters for airport pavements?

3. What about pavement design?4. What is new in airport pavement engineering?

5. Conclusions


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A road can fail a runway can not

Airport pavements must exhibit higher performances than roadpavements and are less tolerant of failures

Which properties should be optimised

What is the reality


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Airport Pavement Desi

Airport pavement specificity

Airport pavement is not as unique as a road!

Apron

Runway

Taxiway

Terminal


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Airport vs. Road

In terms of geometry

Wider, shorter length and low transversal slope

In terms of loadings

Higher load up to 16bars, up to 6 wheels

Low speed on taxiways, high speed on runways

In terms of pavementLower traffic volume 104 instead of 106 cycles

Random in loading application

In terms of serviceability

Skid resistance

FOD

Traffic control


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1. Background


3. What about pavement design?

4. What is new in airport pavement engineering?

5. Conclusions


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Airport pavement functions

Granular base layers

Bound base layers

Top layers

Asset value:Structural need

Cracking

Permanent deformation

Maintenance:Rubber removal

Surface sealantDe-icing

Works under traffic control

Overlay on concrete

Service value:Permanent deformation

Surface ShearSkid resistance

Water evacuation

FOD / integrity

Fuel spilling

Joint sealant


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Airport pavement functions

Granular base layers

Bound base layers

Top layers

Asset value:Structural needCrackingPermanent deformation

Maintenance:Rubber removal

Surface sealantDe-icing

Works under traffic control

Overlay on concrete

Service value:Permanent deformationSurface ShearSkid resistance

Water evacuation

FOD / integrity

Fuel spillingJoint sealant


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Permanent deformation

Degradation on aprons, taxiways, runway entrances

Mainly at aircraft stop lines

Material performances:

Static loading more than dynamic loading

Stiffness at low speed (low frequency)

Low energy dissipation

Suitable solution

Thin asphalt system for top layers (SMA)

High modulus base layer

Polymer modified bitumen PmB


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Strength and structural need

Structural value of the pavement itself

Spread load on sub grade and withstand traffic flow

Valid on aprons, taxiways, runways

Material performance

Stiffness at various conditions


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Master Curve at 15C

100

1000

10000

100000

1,E-03 1,E-02 1,E-01 1,E+00 1,E+01 1,E+02 1,E+03 1,E+04 1,E+05 1,E+06

Shift Frequency

Modulus,

MPa

Asphalt Mix A

Asphalt Mix B

Asphalt Mix C

15C 10Hz

High T

Low frequencyLow T

High frequency


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Master Curve at 15C

100

1000

10000

100000

1,E-03 1,E-02 1,E-01 1,E+00 1,E+01 1,E+02 1,E+03 1,E+04 1,E+05 1,E+06

Shift Frequency

Modulus,MPa

Asphalt Mix A

Asphalt Mix B

Asphalt Mix C

15C 10Hz

High T

Low frequencyLow T

High frequency







Dense asphalt concrete

Depends on the load conditions


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Fuel resistance

Degradation on taxiways, aprons

Due to chemical agent

Can lead to integrity loss FOD

Material performance required:

Fuel resistance

Dense asphalt / closed surface

Special products available

Fuel resisting binder instead of tar


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Airport pavements are specific

Pavement materials have to address key performance parameters

How to predict and characterise these performances

Relevant testing

Under which conditions


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Specification for permanent deformation

For road applications

Wheel tracking test

Dynamic loading

Standard road loading

Creep test static or cyclic

What is suitable for airport applicationsStatic loading

Slow speed related (loading time)

Heavy load, high pressure

French Wheel Tracking Tester

Creep test


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Specification for cracking resistance


Fatigue test

For 1 million cycles

Strain level in range of 60-150 micro strain

Thermal cracking susceptibility

What is suitable for airport applicationsFatigue test

For 10 000 cycles

High strain level in connection with heavy load

Healing effect

Fracture toughness

Fracture toughness

2 points fatigue test


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Elastic modulus (at low strain level)

Indirect tensile strength, ITS at 20C

Full complex modulus measurement

What is suitable for airport applications

High strain maybe not any more in the elastic domain

Need for complex modulus measurement and interpretation

At various conditions especially for slow speed

Look at visco-elasticity of the material


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Fuel resisting material

Common fuel immersion test procedure

Immersion of samples in kerosene

Results compared to dry samples

Mass loss

As a function of immersion time

Less than 1% after 24h

Specimen stability after immersion

Indirect Tensile Strength

Limited use, depend on integrity of specimen

Direct compression StrengthNot less than 75% of strength loss

Specimen mass loss as a function of Kerosine Immersion Time

BBSG 0/10, 5% voids

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80 100 120 140 160 18

Immersion time, h

Specimenmassloss,%


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1. Background




5. Conclusions


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Current approach - ACN/PCN Principle

International system set up by ICAO in Annex 14

ACN/PCN approach

Aircraft Classification Number, ACN

Maximum mass, quality of the soil support, type of structure

Pavement Classification Number, PCN

Comparison of ACN to PCN

The CBR (Californian Bearing Ratio) method

Empirical approach using a simple equivalent wheel

Pavement thickness equivalence & layer equivalency factor per material

Limitation

Based on DC10 as the heaviest aircraft (in correlation with the AASHO road test)

Empirical method based on CBR and material equivalency

Does not take into account material performances


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Effect of super jumbo jets

Introduction of large body aircraft

Bogies of 4 wheels, up to 6 wheels

Aggressiveness of B777, B747, A340, A380

Much higher than small body aircraft

Research program has shown new

pavement failure from bituminous layers


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The new FAA method

FAA has developed a Layered Elastic airport pavement Design (LEDFAA) to comply with large aircraft

body(software available for free)

Bases on multilayered model similar to Shells BISAR

Input

Real traffic flow and load configuration

Elastic modulus of material

Still limitations

Does not take into accountclimate condition (fatigue law)


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Other approaches

Aircraft Loading Index ALI approach

3D Finite Element method

Research & Experiments

National Airport Pavement Test Facility, NAPTF (Atlantic City, US)

Pavement Experimental Programme, PEP (LCPC-Airbus)


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1. Background




5. Conclusions


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Experience sharing FAA (US)

FAA recommendation for bitumen selection (AC 150-5370-10B P401)

Use of the PG grade framework as a reference

In range of PG58 and PG76 for surface layers

PG bump regarding traffic classes for runway, taxiway/Aprons

FAA recommendation for asphalt mix design

Shift from Marshal method to Superpave method

Use of Superpave Gyratory Compactor with Ndesign and Nmax

Some on going research for more fundamental specifications

Fuel resistance sealer and binder (research project 05-02)

Use of Stone Matrix Asphalt SMA (research project 04-04)

Energy ratio approach for assessing fatigue performance at high strain levels (University of Illinois researchpartnership)


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Experience sharing Middle East

Characterisation of permanent deformation

resistance

Model Mobile Load Simulator MMLS from South Africa

Adaptation of the speed and cycle number for airfieldapplication

Introduction of PG82

Greater high temperature criteria to better fit with hot dry climate


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Experience sharing Europe

Airbus research programme

Pavement Experimental Programme 1&2 1998-2003 to assess impact of A380 on pavement (PEP1 bituminouspavement, PEP2 rigid pavement)

Simulation of pavement strain/stress distribution

Cracking performances

PEP 3 to start in 2007 to assess the tyre pressure effect on permanent deformation of asphalt pavement

7 asphalt mixtures to be assessed under various conditions of loading

French BBA, a dedicated asphalt mixture for Airfield application

Gap graded asphalt mixture

Special specification against fatigue cracking and permanent deformation


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1. Introduction

2. Airport pavement similar to road pavement?

3. What are the key parameters for airport?

4. What about specification?

5. Conclusions


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Conclusions

A road can fail a runway can not Airport pavements are different than road pavements

Function, loading, use, operation

Key parameters for airport pavement have greater impact

Static loading

High strain and stress levels

Extreme conditions

Road specifications might be not adapted to suit airfield application

Need for specific dedicated pavement engineering


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Airport Pavement Design

Airport Workshop Lafarge/Shell

10th July 2007, London

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